The present application relates to a secondary battery that includes a cathode, an anode, and non-aqueous electrolytic solution, and to a battery pack, an electric vehicle, and an electric power storage system that use the secondary battery.
In recent years, various electronic apparatuses such as a mobile phone and a mobile information terminal device (a PDA) have been widely used, and it has been demanded to further reduce the size and the weight of the electronic apparatuses and to achieve their longer life. Accordingly, as an electric power source, a battery, in particular, a small and light-weight secondary battery capable of providing high energy density has been developed.
In these days, it has been considered to apply a secondary battery to various other applications in addition to the foregoing electronic apparatuses. Examples of such other applications may include a battery pack attachably and detachably mounted on the electronic apparatuses or the like, an electric vehicle such as an electric automobile, and an electric power storage system such as a home electric power server.
There have been proposed secondary batteries that utilize various charge and discharge principles in order to obtain battery capacity. In particular, attention has been paid to a secondary battery that obtains battery capacity utilizing insertion and extraction or precipitation and dissolution of an electrode reactant. One reason for this is because higher energy density is achieved in such secondary batteries than in a lead battery, a nickel-cadmium battery, etc.
A secondary battery includes a cathode, an anode, and a liquid electrolyte (electrolytic solution). The electrolytic solution includes a solvent and an electrolyte salt. A composition of the electrolytic solution that serves as a medium in charge and discharge reactions largely influences a performance of the secondary battery. Various considerations are therefore made on the composition of the electrolytic solution.
Specifically, in order to suppress degradation in characteristics of an electrochemical device resulting from hydrogen fluoride generated by a decomposition reaction of an electrolyte, an anion component in the electrolyte includes a boron-containing anion (for example, see Japanese Unexamined Patent Application Publication No. 2013-045887).